Apparatus for casting metal articles



, A A j Feb. 25,1941. AD ER 4 2,233,277. .A

- APPARATUS FOR CASTING METAL ARTICLES Filed May 27, 1939 WITNESS I INVENTOR 7 v I Jami/@5355.

ATTORNEYS Patented F eb. 25, 1941 r APPARATUS FOR CASTING METAL ARTICLES Julius Aderer, New York, N. Y.; Edwin Aderer, New York, N. Y., Walter Aderer, Cleveland, Ohio, and Fritz Weckman, Iarchmont, N. Y., executors of said Julius Aderer, deceased, as- .signors to Julius Aderer, Inc., New York, N. Y., a corporation of New York Application May 21, 1939, Serial No. 276,123

1 Claim.

The invention relates to apparatus and method for casting articles such as dental plates, dentures, and the like from the customary molten metals or alloys of which such articles are constituted.

The object of the invention is to supply dental laboratories with means which will assure that the molten metal, at the time that it is forced into the mold,-is in the proper condition with respect to fluidity and temperature. Thus, ii. the molten alloy which is about to enter the, mold cavity is not hot enough to enable it to reach completely the outermost parts 01 the mold cavity before solidifying, the casting will be a failure, and the same thing is true if the alloy is not suificiently free-flowing to fill the mold completely before solidification. There is for each alloy a limited temperature which represents the minimum temperature at which the mold cavity will rectly upon the metal to be melted. In other cases the metal is melted in a crucible through the walls of which the heat from melting the alloy is made effective. In all such instances the operator is compelled to estimate that the metal 'is in a proper condition to be forced into the mold.. That failures frequently occur in such a process is obvious and it is the object of the present invention to provide reliable means by which without guess-work or estimation the alloy will be brought to the proper condition for delivery to the mold when and not until when the molten alloy has acquired the requisite temperature and fluidity. v

. The invention is illustrated in the accompanying drawing in which Fig. 1. is a section of a mold associated with a crucible embodying my invention. Fig. 2 is an enlarged fragmentary sectional view of the outlet portion or the crucible of Fig. 1 with indications of the dimensions of the orifice noted thereon. Fig. 3 is a top view of a m diflerent form of crucible embodying the invention. Fig. 4 is a section on line 4-4 of Fig. 3. Fig. 5 is a view of the crucible of Fig. 3 looking at theexit end thereof. Fig. 6 is a perspective view of a centrifugal type of casting machine ;5 suitable for use in conjunction with crucibles such as are indicated in Figs. 3 to 7, and Fig. '7 is a view partially in section of still another form of crucible.

In Fig. 1 the mold block I, customarily termed the investment is generally a composition of plaster or Paris and powdered'silicon within which is embedded a wax model of the casting to be made and small wax rods to connect the wax model with the pocket 2 of the investment The wax is then completely melted away, which leaves the mold cavity 3 and the sprues or passages I open and ready-to receive the'molten metal. The block I is usually held within aniron The block I is generally heated to a temperature I of about 1200 F. A crucible is then associated v with the mold or vice versa, whereupon alloy material is placed into the cavity of the crucible and melted by the application of heat. When" the operator estimates that the melting has gone far .enough, he lets the moltenalloy flow into the mold. I

In contrast with this ordinary procedure 'I place a crucible 5 upon the investment I (when proceeding in accordance with the method illustrated in Fig. 1), said crucible having a melting pocket 6 and an exit orifice I, the orifice having approximately the dimensions of about 4 mm. diameter at the top, about '3 mm. diameter at the bottom, and a depth of about 4 mm. The cru-- cible is made of graphite, carbon, or other smooth refractory material such as magnesia. The convex cavity 6 is used for conducting the melting process and the dimensions of the small exit oriflce are such that the molten metal will not run out until it has arrived at a temperature and degree of fluidity above the minimum, irrespective of what may be the nature or the melting point 01.- the alloy ingredients. Thus a crucible such as described will serve for a molten alloy whose casting temperature is 1600 F. as well as for an alloy whose casting temperature is 2300" F. 3 The alloy 45 1 material usually consists of several ingredients including gold or precious metals, platinum,;paladium, copper,'silver, etc. The casting itselifi's usually notheavy so that the quantities to be melted in the crucible 5 usually vary from a very 5 little above 5 to perhaps 40 pennyweights. convex cavity 6 of the crucible 5 is about 2 /2 inches in diameter and about A of an inch high above the aperture 1. The alloy to be molten is usually mixed with appropriate quantities of 6B Thei the alloy has a high melting point, by the use of an oxy-hydrogen flame. Electricity can also be .used as a heating medium. In any event, the heat treatment. is continued after the metal is in a molten condition so that its temperatures will continue to be' elevated. At a given moment the molten metal automatically runs freely through the orifice I, whereupon it is forced into the sprues l and into the mold cavity 3 by any suitable available means such as gravity, centrifugal force, pressure, or in some cases suction. At the ordinary melting point of the alloy it will not flow through the aperture 1. A cohesive tendency of the molten metal must apparently be overcome and the addition of more heat accomplishes this end and simultaneously provides the necessary surplus heat. to prevent failure of the molten metal to fill the mold cavity completely. Some of the alloys should have a temperature of at least 1600? F. before being permitted to enter the mold and the described crucible will automatically retain the metal within its own confines until it has at least a temperature of 1600 F.' The temperature may be somewhat higher since limited increase of temperature does not do any harm, but it should not be lower and this is the eifect which is guaranteed by the construction of the crucible 5. Other alloys require temperature of 2300 F. and the same mold in that case holds the material in-the crucible until it has a temperature of at least 2300' E, where- The-passage of the molten alloy through the.

aperture 1, when it does pass through, is relatively fast, with the result that the. cataract maintains the walls of the aperture. clean and unobstructed. The cavity 6 occasionally shows traces of the fluxing material which can be cleaned away, but the aperture I, speaking generally, is not thus afi'ected.

Turning next to. the crucible shown in Figs. 3 to 5, that crucible 5a is constituted of a single block of refractory material having an open top,

'a partially over-hanging section 8, a cavity 611..

a projecting portionil open, at (Fig.5), the lower portion of the opening Ill being above that portion of the cavity in indicated at ll (Fig. 4)

and fluidity have arrived at the proper stage, it

. 75 will gradually flow into the duct 12, whereupon in which the molten metal accumulates. A duct I! having an opening it through its top wall communicates with the lower portions of the molten metal in the crucible. v I

This crucible of Figs. 3 to 5 is adapted for connection with the mold. I illustratedin Fig. 6, the

projecting portion 9 being closely associated with .the-mold admission port 2 of Fig. 6. When the metal is liquefied in'this crucible, it will at first not-enter the duct l2 ,'but when its temperature ejected from the crucible by the centrifugal force.

the molten metal will become visible through the aperture IS. The diameter of the duct I2 is about 3 mm. and with that diameter the molten metal does not flow out of the duct 12 even though it is sufllciently fluid to be ready for injection into the receiving orifice -2 of the mold i. When the operator perceives, through the aperture l3, that the molten metal has I flowed into duct 12, he causes the supporting mechanism M (Fig. 6) to spin on the axis l5 to set up centrifugalmotion sumcient to'force the molten metal contained in the crucible into the mold I. The centrifugal mechanism ll, l5, and including the adjustable weight I 6, is of standard type and need not therefore be described in greater detail except to point out that the easing or saddle I'I serves to supportthe crucible in proper relation to the mold I. When centrifugal motion is thus set-up, the. molten metal in the crucible is initially given a movement transverse to the crucible so that the molten metal climbs up to a position along the side of the crucible which is beneath the overhang 8, said overhang insuring against lateral escape of the molten metal, whereupon the centrifugal motion forces the molten metal in-a direction longitudinal of the crucible and into the receiving orifice 2 of the mold I. In this operation the molten metal which is .in the duct I2 is first withdrawn therefrom due to the transverse movement ofthe metal in the crucible and is then ejected into the mold through the slot ID at a level above the duct l2. The form of the crucible illustrated in Fig. 7 is adapted for the procedure in which the heat is applied through the walls of the crucible rather than by a direct flame impinging against the alloy material. In the crucible 5b of Fig. 7 the alloy is molten in the cavity 6b which is in communication with the exit orifice l8 which passes through a'projection 90. similar to projection 9 of Fig. 3. The orifice l8 inthis case as in the case of the orifice 'Iin Figs. 1 and 2 and the orifice l2 of Figs. 4 and 5 is of such small dimensions that the metal when it is converted into the molten state will not fall through the same until by increased heating the temperature and fluidity of the metal have reached a stage of adequatepreparation for introduction into the mold. 'A peep hole l3 a of smaller 'dimensions than the orifice i8 and therefore more resistant to the flow therethrough of the molten metal,

at the side of the crucible connects-with the pas-.

outlet duct ll for the reasons previously explained but as the metal increases in fluidity and temperature in the cavity 61) it begins to flow into said channel. As the molten metal passes the orifice I31: it will not'fiow throughthat opening for the reasons previously explained but will become visible to the operator and the operator is thereby advised that the metal is ina condition for being elected from the crucible into the mold'and the ejection oi'the metal from's'aid crucible profirst urge the molten metal toward the side of the crucible which is opposite the peep hole Ila whereupon the metal hugging said side-will be Iclaim:

A casting device comprising a melting crucible adapted to contain a charge of material to be alloyed, said crucible being provided with a passage of such limited dimensions that the metal will not flow into said passage until the temperature of the molten alloy is higher than its melting point, said crucible being additionally provided with an exit channel tor'the molten metal above the restricted passage, a centrifugal device for causinga propulsive discharge of the molten metal from the crucible upon acquisition of its higher temperature into a mold, the exit orifice of said channel facing away from the axis or the centrifugal device and the side of the crucible opposite to the direction of movement 0! the crucible by the centrifugal device during ejection of the molten alloy into the mold, being provided with an over-hanging top edge section to guard against escape of molten metal from that side of the crucible.

JULIUS ADERER. 

